1. Field Of The Invention
The present invention relates to a device for preventing stress cracks in concrete slabs, and more particularly but not by way of limitation, to a stress reducing device for preventing stress cracks produced by shrinkage stresses at re-entrant corners of a concrete slab. In one aspect, the present invention relates to a method for reducing stress concentration at a re-entrant corner so as to reduce crack formation in a concrete slab.
2. Brief Description Of The Prior Art
In the building industry one major problem which repeatedly occurs in concrete slabs is the formation of stress cracks at re-entrant corners (i.e., inside corners). Stress cracks occur in concrete slabs as shrinkage stresses increase at re-entrant corners of the concrete slab. That is, as the magnitude of the change in direction of stress increases, the stress concentration at the re-entrant corners of a concrete slab which results in a high incidence of cracks in the slab at re-entrant corners also increases. To reduce stress cracks at the re-entrant corners of a concrete slab, concrete finishers have heretofore chipped the re-entrant corners of a concrete slab in an effort to reduce the sharp edge of the re-entrant corners. While such technique has at times reduced or minimized the formation of stress cracks at re-entrant corners of a concrete slab, such technique is time consuming and has not proven satisfactory in substantially eliminating, on a consistent basis, the formation of cracks at the re-entrant corners of a concrete slab. Therefore, it would be desirable if the shrinkage stresses of the concrete at re-entrant corners of a concrete slab could be effectively reduced or redistributed and thereby substantially eliminate re-entrant corner stress cracks in a concrete slab.